U.S. patent number 6,116,888 [Application Number 09/124,330] was granted by the patent office on 2000-09-12 for prototype mold for blow-molding hollow plastic containers and method of making same.
This patent grant is currently assigned to Owens-Brockway Plastic Products Inc.. Invention is credited to Igor F. Beaufils, Theodore M. Czesak, Richard R. Johnston, Anthony J. Scott.
United States Patent |
6,116,888 |
Johnston , et al. |
September 12, 2000 |
Prototype mold for blow-molding hollow plastic containers and
method of making same
Abstract
Improved blow-molding prototype molding system, method and
apparatus wherein a plastic container is first designed using
computer-aided design (CAD) software to produce a geometric
computer software model of a hollow plastic container of desired
contour. This model is then used to generate a geometric computer
software model of a corresponding mold cavity. This data file in
turn provides the control signal for a cutting tool of a CNC three
axis mold machining tool operating on a starting blank for each
mold half of metal material having predetermined and constant
length, width and thickness outside dimensions. A mold cavity is
thereby automatically machined in a front face of this blank that
constitutes one of the two major and parallel face planes of the
mold half block. The other half of the mold cavity is similarly
formed in the front face of a second mold half block that
cooperates with the first mold block to form the two mold halves of
a complete blow mold. The back faces of each of the mold halves as
well as the top, bottom and two opposite sides remain as initially
provided in the starting blank. Standardized major mold nest
fixture components cooperate in assembly to support, locate, orient
and cool the associated prototype mold halves. The structure of
each mold half is thus reduced to its simplest form.
Inventors: |
Johnston; Richard R. (Toledo,
OH), Czesak; Theodore M. (Perrysburg, OH), Scott; Anthony
J. (Maumee, OH), Beaufils; Igor F. (Holland, OH) |
Assignee: |
Owens-Brockway Plastic Products
Inc. (Toledo, OH)
|
Family
ID: |
22414240 |
Appl.
No.: |
09/124,330 |
Filed: |
July 29, 1998 |
Current U.S.
Class: |
425/195; 249/102;
249/79; 425/522; 425/526; 29/557; 425/812; 29/464 |
Current CPC
Class: |
B29C
33/3835 (20130101); B29C 49/4823 (20130101); B29C
33/04 (20130101); F28F 3/12 (20130101); B29C
33/306 (20130101); B29C 33/3842 (20130101); B29C
33/02 (20130101); B29C 33/303 (20130101); Y10T
29/49995 (20150115); Y10S 425/812 (20130101); B29C
2033/042 (20130101); Y10T 29/49895 (20150115); B29C
49/48 (20130101) |
Current International
Class: |
B29C
33/04 (20060101); B29C 33/30 (20060101); B29C
33/38 (20060101); B29C 49/48 (20060101); B29C
33/02 (20060101); B29C 033/04 (); B29C 049/62 ();
B29C 049/64 () |
Field of
Search: |
;249/79,102
;425/522,526,192R,195,812,183 ;264/401,219 ;29/557,464 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
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|
|
2545133 |
|
Jun 1977 |
|
DE |
|
58-183212 |
|
Oct 1983 |
|
JP |
|
2240300 |
|
Jul 1991 |
|
GB |
|
Primary Examiner: Davis; Robert
Claims
We claim:
1. A method of producing a prototype mold for blow-molding hollow
plastic containers, said method comprising the steps of:
(a) using computer-aided design to produce a geometric computer
model of a container of desired contour,
(b) using said computer container model to design and produce a
software program for controlling a CNC machine to generate a mold
cavity for producing the container of desired contour,
(c) using the software control program in a CNC machine and thereby
machining a plurality of mold portions made of heat conductive
composition and that together have an inner surface complementary
to the desired container contour such that said mold portions can
be operably juxtaposed as two mold halves each having a front face
that cooperates with the front face of the other mold half to form
a mold cavity, and a back face and exterior contour of
predetermined constant geometry,
(d) providing for each said mold half an assembly of mold nest
support components forming a support pocket contoured complemental
to that of said predetermined constant geometry,
(e) assembling each said mold half into the pocket of the
associated assembly of mold nest support components, and wherein
said method comprises the additional step of:
(f) providing a channel for cooling fluid in the pocket of each
assembly of mold nest components for heat-dissipating contact with
the back face of the associated mold half, wherein step (f) further
comprises providing the cooling fluid channel in a manifold plate
component of each nest component assembly against which the
associated mold half is secured in flat face mutual abutment, and
wherein the opposite vertical sides of each mold half are
reinforced by mounting to the manifold plate component a pair of
standoff blocks, one against each such half mold side, to thereby
embrace the half mold laterally while also defining the opposite
side walls of the associated pocket.
2. A method of producing a prototype mold for blow-molding hollow
plastic containers, said method comprising the steps of:
(a) using computer-aided design to produce a geometric computer
model of a container of desired contour,
(b) using said computer container model to design and produce a
software program for controlling a CNC machine to generate a mold
cavity for producing the container of desired contour,
(c) using the software control program in a CNC machine and thereby
machining a plurality of mold portions made of a heat conductive
composition and that together have an inner surface complementary
to the desired container contour such that said mold portions can
be operably juxtaposed as two mold halves each having a front face
that cooperates with the front face of the other mold half to form
a mold cavity, and a back face and exterior contour of
predetermined constant geometry,
(d) providing for each said mold half an assembly of mold nest
support components forming a support pocket contoured complemental
to that of said predetermined constant geometry,
(e) assembling each said mold half into the pocket of the
associated assembly of mold nest support components, and wherein
said method comprises the additional step of:
(f) providing a channel for cooling fluid in the pocket of each
assembly of mold nest components for heat-dissipating contact with
the back face of the associated mold half, wherein step (f) further
comprises providing the cooling fluid channel in a manifold plate
component of each nest component assembly against which the
associated mold half is secured in flat face mutual abutment, and
wherein a backing plate is provided as part of the mold nest
support components and is adapted for mounting to a stock molding
machine platen, and registering alignment of the mold halves in
mold closed condition is provided by mounting alignment pins and
cooperative alignment bushings mounted to said backing plate
independently of the mold halves.
3. A prototype mold apparatus for blow-molding hollow plastic
containers, said apparatus comprising:
a plurality of mold portions that together have an inner surface
complementary to the desired container contour such that said mold
portions can be operably juxtaposed as two mold halves each having
a front face that cooperates with the front face of the other mold
half to form a mold cavity, and a back face and exterior contour of
predetermined constant geometry,
an assembly of mold nest support components forming a support
pocket contoured complemental to that of said predetermined
constant geometry,
each said mold half being assembled into the pocket of the
associated one of said assembly of mold nest support components,
and wherein said mold cavity in each mold half is generated using
computer-aided design to produce a geometric computer model of a
container of desired contour,
said computer container model is then used to design and produce a
software program for controlling a CNC machine to generate a mold
cavity for producing the container of desired contour, and then
employing the software control program in a CNC machine and thereby
machining a plurality of mold portions, wherein said mold portions
are made of heat conductive composition, wherein each said assembly
includes a channel for cooling fluid in the pocket of each said
assembly of mold nest components for heat dissipating contact with
the back face of the associated mold half, wherein said nest
support components include a cooling fluid manifold plate, wherein
said cooling fluid channel is formed in said manifold plate
component of each nest component assembly, the associated mold half
being secured in flat face mutual heat-transfer abutment with said
manifold plate component, and wherein said nest support components
include a pair of standoff blocks, the opposite vertical sides of
each mold half being reinforced by said pair of standoff blocks
being mounted to said manifold plate component, one against each
such half mold side, to
thereby embrace the half mold laterally while also defining the
opposite side walls of the associated pocket.
4. A prototype mold apparatus for blow-molding hollow plastic
containers, said apparatus comprising:
a plurality of mold portions that together have an inner surface
complementary to the desired container contour such that said mold
portions can be operably juxtaposed as two mold halves each having
a front face that cooperates with the front face of the other mold
half to form a mold cavity, and a back face and exterior contour of
predetermined constant geometry,
an assembly of mold nest support components forming a support
pocket contoured complemental to that of said predetermined
constant geometry,
each said mold half being assembled into the pocket of the
associated one of said assembly of mold nest support components,
and wherein said mold cavity in each mold half is generated using
computer-aided design to produce a geometric computer model of a
container of desired contour,
said computer container model is then used to design and produce a
software program for controlling a CNC machine to generate a mold
cavity for producing the container of desired contour, and then
employing the software control program in a CNC machine and thereby
machining a plurality of mold portions, wherein said mold portions
are made of heat conductive composition, wherein each said assembly
includes a channel for cooling fluid in the pocket of each said
assembly of mold nest components for heat dissipating contact with
the back face of the associated mold half, wherein said nest
support components include a cooling fluid manifold plate, wherein
said cooling fluid channel is formed in said manifold plate
component of each nest component assembly, the associated mold half
being secured in flat face mutual heat-transfer abutment with said
manifold plate component, and wherein said mold nest support
components include a backing plate adapted for mounting to a stock
molding machine platen, and said mold nest components further
include alignment pins and individually cooperative alignment
bushings mounted to said backing plate independently of said mold
halves operable for registering alignment of the mold halves in
mold closed condition.
5. A prototype mold apparatus for blow-molding hollow plastic
containers, said apparatus comprising:
a plurality of mold portions that together have an inner surface
complementary to the desired container contour such that said mold
portions can be operably juxtaposed as two mold halves each having
a front face that cooperates with the front face of the other mold
half to form a mold cavity, and a back face and exterior contour of
predetermined constant geometry,
an assembly of mold nest support components including cooperative
water manifolds each forming a support pocket contoured
complemental to that of said predetermined constant geometry,
each said mold half being assembled into the pocket of the
associated one of said water manifolds,
said mold portions being made of heat conductive composition, and
wherein each of said water manifold has an internal channel for
circulating cooling fluid adjacent the pocket of each said manifold
for heat-dissipating heat transfer with the back face of the
associated mold half, wherein each said water manifold comprises a
cooling fluid manifold plate nest support component, and wherein
said cooling fluid channel is formed solely in said manifold plate
component of each nest component assembly, the associated mold half
being secured in flat face mutual heat-transfer abutment in said
pocket of said manifold plate component, wherein said cooling fluid
channel comprises parallel vertically extending blind bores in said
plate joined at alternate ends by horizontal blind bores in said
plate, wherein said manifold plate has a venting fluid channel open
at a peripherally sealed zone of the front area of said manifold
plate pocket, wherein the back face of the associated mold half is
vented and assembled as a vented closure cover for the open zone
area of said venting fluid channel.
6. A prototype mold apparatus for blow-molding hollow plastic
containers, said apparatus comprising:
a plurality of mold portions that together have an inner surface
complementary to the desired container contour such that said mold
portions can be operably juxtaposed as two mold halves each having
a front face that cooperates with the front face of the other mold
half to form a mold cavity, and a back face and exterior contour of
predetermined constant geometry,
an assembly of mold nest support components including cooperative
water manifolds each forming a support pocket contoured
complemental to that of said predetermined constant geometry,
each said mold half being assembled into the pocket of the
associated one of said water manifolds,
said mold portions being made of heat conductive composition, and
wherein each of said water manifold has an internal channel for
circulating cooling fluid adjacent the pocket of each said manifold
for heat-dissipating heat transfer with the back face of the
associated mold half, wherein each said water manifold comprises a
cooling fluid manifold plate nest support component, and wherein
said cooling fluid channel is formed solely in said manifold plate
component of each nest component assembly, the associated mold half
being secured in flat face mutual heat-transfer abutment in said
pocket of said manifold plate component, wherein said pocket of
each said manifold plate component comprises a recess in the front
face thereof with the recess defined by a pair of horizontally
spaced side walls that closely flank and embrace the sides of the
associated mold half to reinforce the same against horizontally
directed stresses generated in the mold cavity during blow molding
and further defined by a back wall with said cooling fluid channel
adjacent thereto internally of said plate, and wherein each said
manifold plate includes a pair of standoff block portions defining
said flanking side walls of said pocket, the mutually opposed
vertical facing surfaces for each mold cavity half being formed by
said pair of standoff block portions oriented co-planar with the
front face plane of the associated said mold half and located
adjacent the proximate side of said half mold to thereby serve as a
standoff mutual abutment in the mold closed condition.
7. The method of claim 1 wherein each standoff block is provided
with a standoff rib having a face co-planar with the front face
plane of the associated mold-half and located adjacent the
proximate side of the half mold to thereby serve as an standoff
abutment in the mold closed condition and as a face vent deflector
plate.
8. The method of claim 2 wherein standoff abutment of the mold nest
components is provided by mounting standoff abutment means on the
mold nest component assemblies independently of the mold halves and
positioned to mutually abut in the mold closed condition to define
the mold closure plane.
9. The apparatus of claim 3 wherein each said standoff block has a
standoff rib with a face co-planar with the front face plane of the
associated said mold half and located adjacent the proximate side
of said half mold to thereby serve as an standoff abutment in the
mold closed condition and as a face vent deflector plate.
10. The apparatus of claim 4 wherein said mold nest components
include standoff abutment means mounted on the mold nest component
assemblies independently of the mold halves and positioned to
mutually abut in the mold closed condition to define the mold
closure plane.
11. The apparatus of claim 6 wherein said cooling manifold plates
are adapted for mounting to a stock molding machine platen, and
together further include alignment pins and cooperative alignment
bushings mounted to said standoff block portions independently of
said mold cavity halves and operable for causing registering
alignment of the mold halves in the mold closed condition.
12. The apparatus of claim 11 wherein said pins and bushings are
constructed and arranged to intersect associated ones of said
horizontal blind bores in the portions thereof entering the
associated manifold plate.
Description
FIELD OF THE INVENTION
The present invention relates to blow-molding hollow plastic
articles, particularly hollow plastic containers, and more
particularly to improvements in prototype tooling for blow-molding
plastic containers and methods for constructing such tooling.
BACKGROUND OF THE INVENTION
In the design and development of new plastic containers, there is
often a need to produce a prototype of a part intended eventually
to be mass produced by blow-molding. Containers of this type are
constructed by placing a parison between two halves of a blow-mold,
closing the mold, and then blowing the parison against the inside
wall surface of the mold. The molds typically used in blow-molding
machines for production purposes are machined from durable and
long-lasting tool steel alloys, and this is a slow and expensive
procedure if it is intended to produce only a few parts to test a
design. For example, it is often desired to construct prototype
containers for showing to customers, or for providing a limited run
of containers. Although conventional prototype tooling and methods
of constructing the same are much less expensive, and require less
time for construction and delivery, than production tooling,
nevertheless such prototype tooling still is fairly expensive and
requires typically several weeks for construction and delivery.
In one type of blow-molding machine, referred to as a shuttle
blow-molding machine, whether single stage or two stage (with both
pre-form and final blow-mold halves), each mold half is carried on
an associated platen displaceable along tie bars by a power means
such as a piston and hydraulic cylinder. Examples of such shuttle
type blow-molding machines are shown in U.S. Pat. Nos. 3,767,747;
3,781,395; 3,978,184; 4,070,428; and 4,118,452. The mold halves
even when constructed for prototype molding purposes are typically
relatively massive and complex structures fastened only at their
back faces to the platen for a cantilever type mounting thereon.
The mold halves themselves are built to withstand both the
compressive and tensile stresses exerted during the molding
operation both in the direction of mold travel as well as laterally
in directions parallel to the closing plane of the mold halves. In
addition, it is necessary to provide liquid cooling for each mold
half and thus involves machining interior cooling channels and
passageways for the cooling fluid in each mold half. Alignment pins
and bushings as well as vent deflectors, are typically also built
into the mold halves.
As pointed out in U.S. Pat. Nos. 5,458,825 and 5,641,448
(incorporated herein by reference), in recent years, one method for
making prototype parts cheaply and quickly has been to first
produce a geometric computer model of the part using computer aided
design (CAD) to create a geometric computer model. A suitable CAD
tool is that known as "PRO/ENGINEER". This model is then used as
input to another software package called "PRO/MOLD" where the core
and cavity portions of the mold are designed, and adjusted for
shrink allowances of a plastic molding process. Both of these
software packages are available from Parametric Technology
Corporation of Waltham, Mass. USA. This produces computer models of
the mold portion or portions. As set forth in the '488 patent, this
computer model then may be used as the control input in a
stereolithographic apparatus (SLA) as a form of solid free form
fabrication. Alternatively, as pointed out in the '825 patent, the
CAD model can be used to generate the control signals for computer
and numerical control (CNC) paths for a cutting tool of a CNC three
axis machining set up to determine the paths for the cutting tool
to follow in cutting an actual single cavity prototype mold from
aluminum or other metal. However, this still can be costly and time
consuming if the prototype mold is designed and constructed along
conventional lines for typical mold halves as mounted in a typical
blow molding machine, and production conditions also are to be
simulated as closely as possible to verify suitability of the
prototype container design so molded.
On the other hand, if in order to save time and money for
prototyping a photo-sensitive polymer or resin is to be used as the
material to make the mold instead of making the mold out of metal,
fewer parts can be molded and with less accuracy than a mold made
of metal such as alloys of aluminum, steel, beryllium copper that
are typically used for production plastic molding.
OBJECTS OF THE INVENTION
Accordingly, an object of the present invention is to provide an
improved method for producing molds for use in production of
prototypes or short run production in conventional blow-molding
apparatus that shortens the time required from initial concept of
the plastic container to be produced to actual prototype run of
parts (for example, to fabricate blow molded parts in one week
after approval of the article drawing generated on a computer) that
is highly flexible and enables rapid changeover of various
prototype molds in the same apparatus, that shortens the mold set
up and take down times of the blow-molding tooling, that is
applicable for blow-molding machines that utilize both a parison
and pre-form, that provides for controlled liquid cooling of the
mold, wherein the complexity of the container design has little or
no impact on prototype mold cost or delivery time, that enables
more parts to be made from a given mold for a short run production,
that more closely replicates production mold tooling and such a
method that is readily convertible to make long production run mold
tooling.
SUMMARY OF THE INVENTION
In general, and by way of summary description and not by way of
limitation, the present invention accomplishes the foregoing
objects by providing an improved blow-molding prototype molding
system and method wherein a plastic container is first designed
using computer-aided design (CAD) software to produce a geometric
computer software model of a hollow plastic container of desired
contour. Then the geometric computer container software model is
used to design and produce, again with suitable software, a
geometric computer software model of a mold for producing the
container of the desired contour. The computer data from the
geometric mold software model is then transferred to a mold maker
(in-house facility or outside vendor) who uses the data file
comprising either the geometric cavity model ("negative") or molded
model container ("positive") to generate a suitable CNC software
control program for use as the control input to generate the
control signals for determining computer numerical control (CNC)
paths for a cutting tool of a CNC three axis mold machining
tool.
The starting blank for each mold half is a simple rectangular block
of metal material having predetermined and constant length, width
and thickness outside dimensions. The three axis CNC machine is
then operated to machine a mold cavity in a front face of this mold
half blank that constitutes one of the two major and parallel face
planes of the block. The other half of the mold cavity is formed in
the front face of a second mold block that cooperates with the
first mold block to form the two mold halves when assembled in the
mold holding carriage fixture of the blow-molding machine. The
usual cavity venting channels are also machined in the front faces
of the mold half blanks. However, the back faces of each of the
mold halves as well as the top, bottom and two opposite sides
remain as initially provided in the starting blank. Moreover, the
usual venting deflector plates and standoff bulwarks or smasher
plate portions are omitted from the prototype mold halves, and
likewise, in some instances, also the usual alignment pins and
cooperative bushings.
On the other hand, the molding machine is further provided with
standardized major mold nest fixture assembly parts that cooperate
in assembly to support, locate, orient and cool the associated
prototype mold halves, and that in turn are supported by the stock
platen of the blow-molding carriage. These major mold assembly
parts include a universal backing plate that allows the set-up to
mount to various types of blow-molding machines and functions as an
adjustable set-up backing plate that serves as an assembly point
for side rails, mold standoffs (or smasher plates) and cooling
water manifold plate components of the mold assembly parts. The
standoffs and/or water manifold mount to the backing plate and
serve as side braces to the associated mold cavity half, and are
also designed to take the brunt of the compression forces otherwise
hitherto exerted by the mold closing ram on the mold halves when
the two halves are clamped together and the machine operated
through a molding cycle. In one embodiment, the mold assembly parts
further include a mold water cooling, open-channel manifold plate
that is sealed to the backside of the mold half. In all
embodiments, heat transfer from the mold cavity is affected via
water cooling channels that are provided in the manifold plate
rather than in the mold halves. The mold manifold plate thus
provides a channel for cooling fluid that is either in direct or
indirect heat dissipating contact with the back face of each mold
half body as operatively mounted in the nest fixture parts.
An important feature of the present invention lies in the fact that
the foregoing standardized nest fixture assembly components may be
re-used for differing prototype molds. That is, the outer
dimensions of the prototype mold halves are of standard
configuration for fitting into the fixture nest even though the
dimensions and contour of mold half cavity machined in each mold
half varies from one prototype mold to the next. In accordance with
another important feature of the invention, the fixture manifold
component has a serpentine cooling water path that conducts water
flowing through this path in direct contact with either the back
face of the mold part or indirect contact therewith to provide
enhanced cooling of each mold half to thereby avoid complicating
the mold half structure with cooling channels. The structure of
each mold half is thus reduced to its simplest form, and instead
most if not all the functions of water cooling, mold orientation,
alignment, structural support, reinforcement against mold closing
and blowing stresses, and adjustment for aligning the two mating
mold halves in operation, is provided for in the standardized and
re-usable major mold assembly nest parts. Thus, mold construction
time is significantly reduced as well as mold machine set-up and
take-down time.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing as well as other objects, features and advantages of
the present invention will become apparent from the following
detailed description of the best mode presently known to the
inventors of making
and using the various embodiments of the invention, taken in
conjunction with the appended claims and accompanying drawings
wherein:
FIG. 1 is an elevational view of a portion of a conventional
shuttle-type blow-molding machine of the prior art as shown in
simplified form;
FIG. 2 is a fragmentary simplified side view of the blow-molding
machine components as viewed from the right in FIG. 1;
FIG. 2A is a fragmentary perspective and more detailed but still
simplified view of the conventional mold halves and associated
backing plates and platens that are shown diagrammatically in FIGS.
1 and 2.
FIG. 3 is an elevational view of one of the prototype mold halves
of the invention as mounted in the nest components of a mold
tooling fixture nest also constructed in accordance with the first
embodiment of the present invention shown as a subassembly by
itself apart from the molding machine;
FIG. 4 is a cross sectional view taken along the line 4--4 of FIG.
3;
FIG. 5 is an exploded perspective view of the mold half and
associated mold nest components of the mold nest subassembly of
FIGS. 3 and 4;
FIG. 6 is an elevational view of the cooling water manifold
component of the nest fixture components of FIGS. 3-5 shown from
the rear side with the cover plate and associated support plate
removed;
FIG. 7 is a cross sectional view taken along the line 7--7 of FIG.
6;
FIG. 8 is an exploded perspective view of a second embodiment of a
mold nest fixture assembly and associated prototype mold half
subassembly also constructed in accordance with the present
invention;
FIG. 9 is an elevational view of a second embodiment of a cooling
water manifold that is a component of the second embodiment fixture
assembly of FIG. 8, but shown by itself;
FIG. 10 is a cross sectional view taken along the line 10--10 in
FIG. 9;
FIG. 11 is a front side elevational view of a third embodiment of
the pin half of a cooling water manifold plate that is a component
of a third embodiment of a mold nest fixture assembly (not
shown).
FIG. 12 is a bottom plan view of the manifold plate of FIG. 11;
FIG. 13 is an elevational view of the right hand side of the
manifold plate of FIG. 11 as viewed therein.
FIG. 14 is a fragmentary cross-sectional view illustrating the
alignment pin and bushing parts interengaged upon closure together
of the pin half and bushing half manifold plates of the third
embodiment cooling water manifold plates carried in two cooperative
mold nest fixtures;
FIG. 15 is a rear side elevational view of the manifold plate of
FIG. 11;
FIG. 16 is an exploded perspective view of a third embodiment of a
mold nest fixture assembly of the invention which is similar to but
a modification of the first embodiment fixture assembly of FIGS.
3-7;
FIG. 17 is a vertical cross sectional view taken along the line
17--17 of FIG. 16;
FIG. 18 is a perspective assembly view of a fourth embodiment of a
mold nest fixture assembly of the invention which is similar to but
a modification of the second embodiment fixture assembly of FIGS.
8-10;
FIG. 19 is a front elevational view of the fixture assembly of FIG.
18;
FIG. 20 is a cross sectional view taken on the line 20--20 of FIG.
19;
FIG. 21 is a front elevational view of the modified water manifold
nest plate employed in the fourth embodiment mold nest fixture
assembly of FIGS. 18-20; and
FIGS. 22 and 23 are cross sectional views taken respectively on the
lines 22--22 and 23--23 of FIG. 21.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
General Arrangement of One Type of Shuttle Blow Molding Machine
FIGS. 1, 2 and 2A illustrate in simplified and diagrammatic form
one half of a two shuttle set-up commonly used in one type of
typical blow molding shuttle machine that generally conforms to a
single cavity blow molding operation shown and described in the
aforementioned U.S. Pat. No. 3,767,747, which is incorporated
herein by reference. Similar apparatus set-ups are shown in the
aforementioned U.S. Pat. Nos. 3,781,395 and 3,978,184, also
incorporated herein by reference. The set-up includes an extruder
station A having a conventional extruder 20 that provides a
well-known and so-called "free-extrusion" blow molding mode of
operation wherein a pendant tube of thermoplastic material issues
from a downwardly facing orifice to provide the extruded tube 22
for forming a parison. The blow molding machine also includes a
blow molding station B wherein a blow pin assembly 24 of
conventional construction includes a blow pin 26 vertically movable
into the upper entrance of closed mold halves when positioned
therebelow. The machine also includes the blow mold carriage
assembly 30 having a fixed outer platen 32 supported at the outer
ends of a pair of tie rods 34 and 36 in the usual fashion. An inner
platen 38 is slidably supported on the tie rods and is moved by the
piston 40 of a ram 41 mounted on the framework of the blow mold
fixture carriage assembly 30. It will be understood that another
companion carriage assembly (not shown) and another blow molding
station (not shown) are arrayed to the left of station A.
In accordance with conventional prior practice, the blow mold
assembly fixture carriage 30 supports a blow mold in the form of
cooperative blow mold subassembly halves 42 and 44 respectively
mounted on platens 32 and 38 (FIG. 2). When a blow mold assembly 30
is brought into position adjacent the extruder station A, a
parison-forming pendant tube 22 of heated thermoplastic material is
extruded between the open set of mold halves 42 and 44. Platen 38
is moved to close mold halves 42 and 44 together on the pendant
tube 22 hanging from the extrusion orifice, this closure of the
mold halves thereby pinching the bottom of the tube shut to form a
blowable bubble or parison.
The tube entrapped in the mold halves is then moved with the mold
carriage assembly 30 laterally and vertically away from the
location of the extruder 20 to an operative position at the blow
station B (FIG. 1). The blow tube 26 is inserted into the portion
of the parison tube protruding from closed mold halves 42, 44 and
air under pressure is introduced into the palison to inflate the
same to the configuration of the mold cavity defined by the closed
mold halves 42, 44. During the blowing of the body of the container
and during the residence time thereof in the mold, the same is
being cooled, as by the provision of coolant channels provided in
each of the mold halves and communicating with a liquid coolant
supply circuit of the associated backing plate in the usual
fashion. Thus, it will be seen that the blow mold 42, 44 of the
prior art is typically constructed to be rugged, fairly complex,
self-sustaining axially in the direction of mold closure to
withstand the mold closure compression forces developed by
operation of ram 41, as well as self-sustaining laterally in stress
planes parallel to the closing plane of the mold developed during
mold blowing. Hence, even when being constructed only for use as
prototype tooling, the blow mold 42, 44 is relatively costly and
time consuming to construct and install in the blow mold fixture
carriage assembly 30 of the blow mold machine.
FIG. 2A illustrates in somewhat more detail the components of the
conventional mold half subassemblies 42 and 44 in mold open
condition. These components as labeled A-K in FIG. 2A are
identified and their respective function outlined as set forth in
the following TABLE 1:
TABLE 1 ______________________________________ FIG. 2A-MOLD PARTS
______________________________________ A-Anvil-(striker plate) Sits
in a pocket on top of the finisher insert. A pair of platens forms
the top of the finish and supports the parison as the moil is being
formed. B-Finish Insert A tooled surface that determines the size
and shape of the finish on the container. C-Alignment Bushing
Telescopically receives associated alignment pin upon mold closure.
D-Pin Hole Vents Small openings in the wall of the mold cavity.
They are optional and have the same function as face vents. E-Face
Vents Grooves in the mold face. They allow air to escape from the
space between the parison and the walls of the mold cavity as the
parison expands to form a container. F-Mold Cavity Determines the
size and shape of the container. G-Deflector Plate Directs air that
escapes from the mold cavity through the vents away from newly
forming parisons. H-Bottom Plate Along with the pinch off area
forms the base of the container by pinching the parison closed when
the mold closes. It seals the bottom of the parison before the
container is blown. I-Alignment Pin Telescopically engages
associated alignment bushing upon mold closure J-Mold Platen
Support the backing plates. Plates are part of the carriage
assembly rather than of the mold assembly K-Backing Plate Supports
each mold half. Water lines run through the backing plates.
______________________________________
First Embodiment Prototype Mold Assembly and Method of Making
Same
Referring to FIGS. 3, 4 and 5, one half of a blow mold fixture
assembly 50 constructed by way of example in accordance with the
method of invention is substituted for the prior art conventional
blow mold half subassembly 44 and is adapted to be mounted on and
carried by the platen 38 of the molding machine carriage fixture
30. The mold half tooling fixture assembly 50 is made up primarily
of standardized, universally usable fixture components comprising a
backing plate 52; a cooling water manifold subassembly 54 made up
of a water manifold plate 56, a water manifold cover plate 58, and
a water manifold support plate 60; a right side pin rail 62, a
bottom side pin rail 64 and a left side pin rail 66; a right side
mold standoff (or smasher plate) 68 and a left side mold standoff
(or smasher plate) 70, a mold finish half 72 and an anvil 74; and a
mold cavity half 76. Platen 38 is a stock item provided on any
given type of blow-molding machine as the principal support member
for the associated half of the blow mold assembly. The "nest"
components 52-70 are of preselected standard configurations that
when assembled provide water cooling manifold and coolant circuitry
components as well as support for the associated prototype mold
half subassembly 72-76 in a "nesting" space as defined laterally
between standoffs 68 and 70 and at the rear by the front surface of
water manifold 56. The associated rectangular mold half section 76
has preselected standardized outside orthogonal dimensions designed
to fit this nesting space regardless of the particular
configuration of the mold half cavity 78 formed in the starting
block workpiece from which section 76 is machined to form cavity
78. Hence, the remainder of the fixture components 52-70 of the
half mold nest can be used for different mold cavity geometries
without changing the setup of the nest components 52-70 themselves
relative to one another or the entire nesting assembly relative to
the platen 38.
The back plate 52 is a heavy duty structural member and is provided
with a predetermined pattern of tap-threaded through-holes
extending with their axes perpendicular to the major planes of back
plate 52 and platen 38 in assembly so that back plate 52 can be
mounted to differing platens of various blow molding machines, thus
rendering back plate 52 and the associated nest components
universally mountable in blow molding machines equipped with
differing platens in their blow mold carriage fixtures.
As best seen in FIGS. 4 and 5, back plate 52 also serves as the
inlet and outlet conduit for supplying cooling water to the water
cooling chamber of the manifold plate subassembly 54. To this end,
a horizontally extending inlet passage 90 is drilled and bored
internally to connect with two vertically extending internal branch
passageways (not shown) that communicate in turn with left and
right supply ports 92 and 94 that open in the front face of plate
52 near its upper edge, and which are suitably countersunk to
receive sealing O-rings 96 and 98 respectively. Likewise, a main
horizontal outlet passageway 100 is machined to extend horizontally
of plate 52 below passageway 90 and parallel thereto to communicate
with a pair of return ports (not shown) opening in the front face
of plate 52, and similarly countersunk and provided with O-ring
seals.
Backing plate 52 also serves as the mounting framework for the
water manifold subassembly 54 (parts 56-60) as well as for the
pin/bushing side and bottom rails 62, 64, 66. For this purpose,
suitable fastener-body receiving openings are provided in the rails
for registry with the corresponding openings in the front face of
plate 52 to provide for removable attachment of these nest
components by socket head cap screws 101, 103, 107, 109, 111 and
113 to the front face of the backing plate 52 (FIG. 3). A series of
vertical and horizontal keyways, such as keyways 104, 106, 108, 110
and 112 (FIG. 5) are provided to receive precision locating
alignment key stock therein to both reinforce the attachment
mounting of these components to backing plate 52 as well as to
insure precision location of the components thereon.
The rails 62, 64 and 66 carry cantilevered mounted, telescopically
engageable protruding, alignment members, either in the form of
pins or pin-receiving bushings. In the embodiment illustrated by
way of example in FIGS. 3-5, these alignment members are shown as
alignment pins 114 and 116 on right side rail 62, alignment pins
118 and 120 on bottom rail 64, and on left side rail 66, one
alignment pin 122 (FIG. 3). It is to be understood that FIG. 5
illustrates only one half of a complete first embodiment mold
fixture assembly, the other half (not shown) being a mirror image
of what is shown in FIG. 5. The half mold fixture assembly 50 would
take the place of the prior mold half cavity subassembly 44 of
FIGS. 1, 2 and 2A for mounting to the rear platen 38 of the
carriage fixture 30. In this example, this mirror image mold nest
assembly (not shown) would have its side and bottom rails equipped
with cooperative alignment bushings that are oriented to
telescopically receive the associated alignment pins 114-22 of
assembly 50 that protrudes from the side and bottom rails 62, 64,
66 when platen 38 is moved to mold closed position. The
telescopically interengaged pins and bushings thus insure precise
alignment of the mold cavity halves of each nest in the mold closed
condition, and can be easily adjusted without altering the set-up
of mold section 74 in its nest
The water manifold subassembly 54 (shown in cross section in FIG.
4) is made up of the water manifold plate 56, cover plate 58 and
backing plate 60, these three parts being shown exploded from one
another in FIG. 5 and the water manifold plate 56 being shown by
itself in FIGS. 6 and 7. As best seen in comparing FIGS. 4 and 6,
the back side of water manifold plate 56 is provided with a large
rectangular cavity defined by top and bottom walls 130 and 132 and
side walls 134 and 136 and a recessed planar surface 138 inset from
the rear marginal face 140 of plate 56 slightly over half the
thickness of the plate (FIG. 4). Three vertically arrayed
side-by-side water channel serpentine passageways 150, 152, 154 are
formed by milling into recessed surface 138 serpentine grooves 156,
158, 160, respectively, leaving alternating left and right
projecting cooling fins oriented parallel to one another and spaced
vertically apart in each
serpentine row, as illustrated by the fins numbered 162 and 164 in
row 150 in FIG. 6.
As shown in FIG. 4, the water manifold channel grooves 150, 152,
154 are closed on their back side by cover plate 58 that fits
closely within the confines of the recess walls 130-136 and flat
against surface 138. A continuous peripheral weld 168 secures cover
plate 58 in manifold plate 56 and is made to water-tight
specifications. Support plate 60 is tack welded to the back side of
cover plate 58 prior to assembly to manifold plate 56. After the
subassembly of support plate 60 and cover plate 58 has been welded
in place, a central horizontal keyway groove 170 (FIG. 4) and an
intersecting central vertical keyway groove 172 are milled in the
back side of support plate 58, and continuations of the ends of
each of these grooves are likewise milled in the back face of
manifold plate 56. Suitable keys 174 and 176 register in backing
plate keyway 104 and support manifold plate keyway 172 for
precision lateral positioning of these two components relative to
one another. The water manifold subassembly 54 is detachably
fastened to the front face of backing plate 52 by four socket head
cap screws, such as cap screws 178 and 180 (FIG. 5) individually
inserted through one of the associated four corner mounting holes
182, 184, 186, 188 (FIGS. 5, 6 and 7).
The passageways for admitting liquid coolant to the serpentine
cooling groove arrays 150, 152 and 154 and for exhausting coolant
fluid therefrom are formed by drilling horizontal blind bores 200
and 202 in the top and bottom solid margins of manifold plate 56.
Each of these bores is then sealed closed by a plug disk seal
disposed interiorly of but adjacent the associated cap screw
mounting holes 182 and 184 (disk seal 204 for bore 200 being shown
in FIG. 7). Coolant fluid is admitted to the upper cross channel
bore 200 via entrance ports 206 and 208 that respectively register
with backing plate supply ports 92 and 94 when manifold subassembly
54 is assembled to plate 52 as described previously. Water is
exhausted from bottom blind bore 202 via exhaust passages 210 and
212 that register with associated return ports in the front face of
backing plate 52 that in turn communicate with backing plate
coolant return bore 100.
Four right angle connecting passageways are provided to feed
cooling water from bore 200 to the top groove of each manifold
serpentine array 150, 152 and 154. More particularly, and as seen
in FIG. 6, four horizontal blind bores 220, 222, 224 and 226 are
drilled into the back face of manifold plate 56 so as to intersect
both sides of the lower reach of bore 200. Bores 220-226 then
perpendicularly intersect at their inner ends corresponding
vertical drilled passages 228, 230, 232 and 234 that are drilled
downwardly from the top edge surface of plate 56 and open into the
uppermost leg 156 of serpentine passageway 150 to thereby feed
inlet cooling water into serpentine passageway 150 at the upper end
thereof. The entrance ends of bores 220-226 are plugged where they
intersect the rear face 140 of manifold plate 156, and likewise the
ends of passageways 228-234 are plugged where they intersect the
upper edge surface of plate 56. As will be seen from FIGS. 6 and 7,
the central serpentine groove passageway 152 likewise is fed by
four right angle passageways, and likewise as to the right-hand
serpentine groove passageway 154.
The lowermost excursion legs of serpentine groove passageways 150,
152 and 154 are similarly communicated to drain channel bore 202 by
four right angle connecting passageways for each of the three
passageways.
The right and left mold standoffs 68 and 70 are individually
fastened by associated set of five cap screws 250 and 252 (FIG. 3)
that individually thread into associated tapped mounting holes
provided in the front face of manifold plate 56. Precision lateral
alignment of each standoff 68, 70 with its mounting position on
manifold 56 is assured by a pair of keys 254 and 256 secured by
fasteners in keyway slots provided therefor in the front surface of
manifold plate 56. Keys 254 and 256 register with a keyway 258
provided in the back side of standoff 68 (FIG. 5). Left standoff 70
likewise has a keyway groove 260 for receiving a left hand pair of
keys fastened in keyway slots in the front face of plate 56, only
upper key 262 being visible in FIG. 5.
With the standoffs 68 and 70 so mounted, the mutually facing side
surfaces 266 and 268 of standoffs 68 and 70 respectively, in
cooperation with the planar front surface 270 of manifold plate 56,
are designed to form precision side flanking and rear abutment
surfaces to define a "nest" of predetermined width and depth
dimensions for precision-fit receiving the mold cavity half 76. The
back side of mold half block 76 is flat and planar (FIG. 4) and
abuts surface 270 in flat face-to-face contact and is drawn tight
thereagainst by six cap screws 272-282 (FIG. 3) threaded into six
associated tapped mounting holes 283 provided in the front face of
manifold plate 56. The parallel side surfaces 284, 286 of block 76
seat snugly against standoff side surfaces 266 and 268 respectively
in assembly therewith on manifold plate 56.
It is to be noted that the respective front "smasher plate" faces
69 and 71 of standoffs 68 and 70 are recessed relative to
respective associated integral standoff rib portions 73 and 75 of
standoffs 68 and 70. Rib portions 73 and 75 provide continuations
of associated standoff side surfaces 266 and 268 that terminate
flush with the plane of the outermost face surfaces 77 of block 76.
The usual mold cavity venting grooves 79 are recessed rearwardly
from face surfaces 77 and thus rib portions 73 and 75 serve as
deflectors in place of the built-in mold cavity defector plates of
the prior art conventional mold halves 42 and 44 referenced in FIG.
2A. Standoff rib portions 73 and 75 also are precision machined to
provide flat abutment surfaces 81 and 83 that cooperate upon mold
closure with corresponding standoff rib portions provided in like
manner on the companion mirror-image mold nest fixture assembly
(not shown) that mounts on outer platen 32. Hence, the mold-closing
compression forces exerted by ram 41 during complete mold closure
are taken as reaction compressive stress (in the direction of mold
travel) by standoffs 68 and 70 rather than by the material of mold
block 76.
The mold finish 72 is secured by two socket head cap screws 290 and
292 that thread into the upper surface of block 76. Anvil part 74
is fastened by four cap screws 294 that thread into mounting holes
in the recess provided for anvil 74 in the upper surface of finish
mold sections 72. It is to be understood that the finish mold
section 72 and associated anvil 74 is often re-usable in
conjunction with containers of differing contour, and hence may not
need to be specially made for each prototype mold.
It will thus be seen that, in accordance with the invention, the
outer dimensions of any given half mold block 76 are maintained
constant and adapted to precision fit between the standoffs 68 and
70. Accordingly, such prototype mold halves may each have a
different mold half cavity 78 formed therein as desired for molding
a given prototype container shape without thereby requiring any
change in the structural supporting and cooling components 52-74 of
the mold nest assembly 50, nor in their set-up adjustment in
assembly to their associated blow molding machine platen. The nest
components 52-74 may thus be reused for differing prototype molds
76 because the outer dimensions of each prototype mold 76 are a
standard configuration for fitting into the standard-sized nest
provided by standoffs 68 and 70 and the associated front face 270
of manifold plate 56.
Second Embodiment Half Mold and Nest Assembly
FIGS. 8, 9 and 10 illustrate a second embodiment of a half mold and
nest assembly 300 also constructed in accordance with the method
and apparatus features of the invention. Assembly 300 includes as
its principal components a stock platen 38' which may be
constructed similar to platen 38 described previously, or
alternatively that may be constructed in the form of a universal
backing plate as shown and to incorporate a fastening system that
enables mounting to various blow molding machines. Assembly 300
also includes a backing plate 302 that serves as the assembly point
to the universal backing plate 38' for further assembly of next
fixture components comprising a pin side rail 304, a bushing side
rail 306 and a mold cooling water manifold plate 308. The remaining
assembly components comprise the mold finish half plate 72,
associated anvil 74 and a modified mold cavity half block or plate
76' corresponding to mold cavity half 76 described previously.
Backing plate 302 detachably mounts to plate 38' by means of a
plurality of socket head cap screws, one of such screws 310 being
seen in FIG. 8. Mold manifold plate 308 is detachably secured to
backing plate 302 by four cap screws, two of such cap screws 312,
314 being seen in FIG. 8. Accurate horizontal alignment of manifold
plate 308 on backing plate 302 is assured by a vertical key 316
mounted in an associated keyway 317 in plate 302 and that is
received in a companion keyway 318 in block 308. Vertical alignment
is provided by horizontal keys 320 and 322 mounted in backing plate
keyway 346 and received in a horizontal keyway 324 provided in the
back side of block 308.
Pin side rail 304 mounts to plate 302 adjacent the right side of
block 308 by a clamp-type system comprising a pair of horizontal
dovetail grooves 326 and 328 in plate 302 that slidably receive
corresponding dovetail keys 330 and 332 in turn attached by cap
screws 334 and 336 to pin rail 304. An alignment key 338 is secured
by screw 340 to a keyway 342 in the back side of pin rail 304 so as
to slidably mate in the keyway 346 of plate 302. Pin rail 304 also
includes a pair of alignment pins 348 and 350 each having a shank
352 and 354 which are inserted through corresponding through-bores
356 and 358 in pin rail 304. Pins 348 and 350 are captured in the
associated rail by the head 360 of each pin seating between a
counterbore in the rear end of bore 356, 358 and the front face of
plate 302 in the mounted condition of pin rail 304 on plate
302.
Pin rail 304 also carries a pair of standoff abutment rods 362 and
364 cantilevered mounted in sockets 366 and 368 in the front face
of rail 304 by associated cap screws 370 and 372 extending
coaxially through the respective rails.
Bushing side rail 306 is similarly mounted to plate 302 by a pair
of dovetail keys 376 and 378 received in grooves 326 and 328,
respectively, and attached by cap screws 380 and 382 to rail 306.
Rail 306 also carries a pair of standoff rods 384 and 386 mounted
thereto in the manner of rods 362 and 364. The end face protrusion
(abutment plane) distance of each standoff rod 362, 364, 384, 386
is precision adjusted by use of suitable shims 388. Bushing rail
306 has a pair of larger diameter through-bores 390 and 392 that
individually receive hollow alignment bushings 394 and 396. The
head flange 398 of each of these bushings is likewise captured
between a counterbore in each of the bores 390 and 392 (not shown)
and the front face of plate 302 in the mounted condition of rail
306.
It will be understood that the other companion mirror-image mold
nest assembly carried on the opposed platen of the carriage fixture
of the molding machine, and that cooperates with assembly 300 in
forming the complete mold system, is set up with its pin rail and
bushing rail coaxially aligned with pin rail 304 and bushing rail
306 so that the pin shanks 352 and 354 are slidably received in the
corresponding bushings of the other mirror image mold nest during
mold closure. Similarly, the standoff rods 362, 364, 384 and 386
are coaxially aligned with similar standoff rods on the mirror
image cooperative mold half nest assembly to control abutment
closure position of the two mold halves, and to absorb as
compression reaction stresses most of the mold-closing forces, in
the closed condition of the complete mold assembly on the molding
machine carriage.
Mold cooling water manifold plate 308 has a recessed nest or pocket
formed in its front face by a planar back surface 400 recessed
rearward from the flanking front end faces 402 and 404 of block 308
and extending in a plane parallel to the back face 406 of block 308
(FIGS. 8, 9 and 10). The sides of the pocket recess in block 308
are defined by parallel sidewalls 408 and 410 that are spaced from
one another by a constant predetermined design distance. The mold
cavity half block 76' likewise has a predetermined set of outside
dimensions such that its parallel sidewalls 412 and 414 have a
constant predetermined spacing widthwise of block 76' so as to fit
with a precision snug sliding fit in the pocket of block 308 and
against the pocket sidewalls 408 and 410, respectively. The flat
back wall (not shown) of mold block 76' abuts flat against the
recess surface 400 of the pocket when it is drawn tightly
thereagainst by tightening down the mold block mounting cap screws
416-426 that are threadably received in associated tapped mounting
holes 428-438 (FIGS. 9 and 10) provided in face 400 of the pocket.
Manifold block 308 thus supports the mold cavity block 76' and
also, like standoffs 68 and 70, reinforces it laterally to help
resist forces exerted on the mold cavity walls during parison blow
in the molding cycle.
The cooling of the mold cavity, after blowing the hot parison
therein, is accomplished by providing a liquid coolant circulating
passageway system with inlet and outlet supply passages in the
backing plate 302 feeding a serpentine coolant passageway 440
formed as a further recess of constant depth in recessed pocket
surface 400 (FIG. 10) and following the serpentine path as shown in
elevation in FIG. 9. Coolant supply lines are connected to
associated ports 442 and 444 provided in the side of backing plate
302 that feed backing plate internal passages (not shown) so as to
supply water out of an O-ring sealed port 446 (FIG. 8) into an
inlet port 448 (FIGS. 9 and 10) in the back face 406 of block 308.
Port 448 is connected by a vertical passage 450 to an inlet port
452 feeding into the upper entrance leg 454 of passageway 440. A
circumferentially continuous O-ring groove 456 is milled in face
400 so as to completely encompass the serpentine passageway 440
(FIG. 9) and receives an 0-ring 458 (FIG. 8) that seals the back
face of block 76' when clamped thereagainst in assembly to serve as
a cover to close the open face of passageway 440. Hence, coolant
flows directly against the back surface of block 76' as it makes
its excursion through passage 440 from inlet 452 to an outlet 460
at the end of the bottom-most leg 462 of passageway 440. Outlet 460
registers with a port 464 in the front face of plate 302 (FIG. 8)
which communicates with internal passageways therein to exit at
port 444.
Method of Producing Prototype Mold Assemblies 50 and 300 and Mode
of Operation of Same
With the foregoing description of the structure and function of the
components 52-74 and 302-308 of each respective half mold assembly
nest 50 and 300 and associated half mold cavity blocks 76 and 76'
in mind, it will now be better understood how the improved
blow-molding prototype molding system and method of the invention
shortens the time from initial concept of the plastic container to
be produced to actual prototype run of parts. In accordance with
the invention, a plastic container is first designed as desired
using computer-aided design (CAD) to produce a geometric
electronically-recorded computer model of a hollow plastic
container of desired contour. This is accomplished using the
aforementioned conventional software programs. If desired, this can
be transferred into a plastic mock-up of the container using one or
more of the aforementioned prior art rapid prototyping systems.
However, typically the computer terminal orthogonal and
three-dimensional rotatable graphic display is adequate to verify
to the container designer that the program has produced the proper
computer model of a container of desired contour. The geometric
computer container model is then used (either as a positive
computer container image directly, or indirectly via a negative
computer cavity image) to design and produce, with suitable
software, a geometric computer model of a mold cavity 78, 78' to be
machined in the starting blank block that is to be employed to
produce the mold half cavity block 76, 76' for blow molding the
container of the desired contour. This computer data for generating
the geometric mold cavity model is then transferred to a mold
making facility (either on computer diskette or via direct on-line
hook-up) that uses this data file, comprising the geometric
computer container model or mold cavity model, as the control input
data to be converted into a CNC software control program that in
turn is used to generate the control signals for determining the
computer numerical control (CNC) paths for a cutting tool of a
conventional CNC three axis mold machining tool to machine the half
mold cavity.
As will be evident from FIGS. 3-5 and 8, the starting blank for
each mold half 76, 76' is a simple rectangular block of metal
material, such as a suitable alloy of aluminum, steel, or beryllium
copper, etc., having a
predetermined length, width and thickness outside dimensions. The
width dimension conforms to the spacing between the flanking side
surfaces 266 and 268 of the right and left side wall standoffs 68
and 70, respectively, or between the surfaces of the sidewalls 408
and 410 of the nest recess pocket of mold water manifold plate
308.
The CNC machine thus is automatically controlled to machine the
mold cavity 78 or 78' in the front face in this mold half blank,
this front face constituting one of the two major and parallel face
planes of the starting block. The other half of the mold cavity is
formed in the front face of a second mold starting block that is
intended to cooperate with the first mold block to form the two
mold halves when assembled in the associated nest assemblies 50 or
300 and installed on the opposed platens of the carriage fixture 30
of the blow molding machine as described, for example, in
conjunction with FIGS. 1 and 2. It is to be noted that the back
faces of each of the molds halves 76, 76', as well as the top and
bottom and two opposite sides thereof, remain as initially provided
in the starting blank. The only further machining required to
produce the finished mold half blocks is the front face vent
recesses 79, 79', the holes for the cap screw fasteners 272-282 or
416-426, as well as those for mounting the finish plate 72 with cap
screws 290, 292.
In accordance with the method, the molding machine is provided, in
place of the conventional prior art mold set-ups 42 and 44 of FIGS.
1-2A, with the major mold assembly components 52-74 of the nest
assembly 50 of the first embodiment or components 302-308, 72, 74
of the next assembly 300 of the second embodiment. The nest fixture
components cooperate in assembly as a fixture support for the
prototype mold half cavity part 76, 76' when supported as an
assembly by the stock platens 32 and 38 of the blow molding
carriage 30. These major mold assembly parts thus include the
universal backing plates 52, 302 that allow the set-up to mount to
various types of blow molding machines. This adjustable set-up
backing plate, on its front side, serves as an assembly point for
side rails 62 and 66, bottom rails 64 in assembly 50, and for pin
and bushing rails 304 and 306 in assembly 300. The backing plates
also serve as an assembly point and support for the manifold plate
components 56, 308, as well as, in the first embodiment, right and
left standoffs 68 and 70. Standoffs 68 and 70 in assembly 50 and
water manifold 308 in assembly 300 securely mounted to the
associated back-up components of the nest assembly and serve to
side brace the associated mold cavity halves 76, 76'. Hence, these
nest components are designed to take the brunt of lateral expansion
forces exerted on the mold half when the two halves are clamped
together in the molding machine and operated through a molding
cycle wherein the mold cavity is subjected to the blow molding
fluid pressure. Moreover, the right and left standoffs 68 and 70 in
assembly 50 and the standoff rods 362, 364 and 384, 386 in assembly
300 are designed to absorb the brunt of the mold closing
compression forces exerted by ram 41 in the direction of mold
travel when the two halves are clamped together in the closing of
the mold fixtures for operation in a molding cycle. The alignment
pins 114-122 or 348, 350 and associated bushings are also securely
and accurately oriented on the adjustable backing plate, separate
from the mold cavity halves, rather than being built into the mold
cavity halves as in the prior art mold assemblies described in
conjunction with FIGS. 1-2A. The deflector plates in the first
embodiment assembly 50 are also built in to the right and left
standoffs 68 and 70 and thus are no longer required to be made as a
component of the mold cavity half part.
In addition, it is to be noted that the mold cavity half block also
is devoid of any water cooling channels, the mold cooling function
having been transferred to the mold manifold plates 56 in assembly
50 and to manifold plate 308 in assembly 300. In assembly 300, the
mold manifold plate 308 has open serpentine water conducting
channels that are sealed by the back side of mold half 76', whereas
manifold plate 56 is a sealed unit in assembly with backing plate
52 and thus function as a coolant carrier independently of mold
cavity half 76. In both cases, the water manifold plate 56, 308
provides heat transfer from the mold cavity through the metal of
the half mold cavity block to the water cooling channels that are
provided in the manifold plates 56, 308 rather than in the mold
cavity half parts. The backing plate is provided with supply and
return passageways for the coolant fluid that communicates in
assembly with the manifold plates, if it is desired to remain in
keeping with the conventional use of the backing plate to provide
the hook-up to the water lines for cooling the mold halves.
In the first and second embodiment assemblies 50 and 300, the mold
cavity half consists two parts: (1) main body part 76, 76' of the
mold half having the aforementioned predetermined outside
dimensions in a rectangular starting block; and (2) a finish mold
section 72 (with its associated anvil 74) affixed to the top side
of the mold body block. Preferably, the mold maker provides the
main body part for the two mold halves, whereas the finish mold
section 72 is often reused by the molder in conjunction with
containers of differing contour. In some instances, each mold half
will also be sub-divided further so that it is made in three parts,
i.e., by having a heel mold section designed to flush abut the
bottom side of the body block rather than being integrated as shown
in conjunction with half mold cavity block 76, 76'. In this
alternative construction, the mold maker would also provide the
heel section because it includes a portion of the mold cavity
design to be CNC machined, and typically varies with each variation
in contour body shape.
It will thus be seen that an important feature of the present
invention lies in the fact that the prototype molding system
provides standardized elements in the molding machine fixture that
may be reused for differing prototype molds. That is, the outer
dimensions of the prototype mold halves 76, 76' are of standard
configuration for fitting into the standardized nest set-up
provided by the remaining components of the fixture even though the
dimensions and contour of the mold cavity 78, 78' varies from one
prototype mold to the next. Moreover, the construction of the mold
cavity half blocks is simplified by divorcing from the mold cavity
half block the structure of the prior art that serves to align the
two mold halves, that serves as mold standoffs to absorb closing
forces in compression in the direction of mold closing travel, that
serves to cool the mold cavity half parts, to align the mold halves
when closed together and to deflect mold venting gasses. This
feature enables the structure of each mold half to be reduced to
its simplest form, and to transfer all the functions of cooling,
orientation, alignment, static structural support, reinforcement
against dynamic and static molding stresses, and adjustment for
aligning the two mating mold halves in operation to the major mold
assembly nest parts. These components can then in turn be better
optimized to perform their respective functions without being
design comprised by the necessity of integration into the mold
cavity half block. This features also enables the prototype mold
construction time to be significantly reduced, and also reduces the
time required for molding machine set-up and take-down. Also, due
to the simplification of the mold cavity half parts 76, 76', the
same can be machined from more durable material even though only
designed for prototype or short pilot run production without
thereby increasing the overall expense, and yet making it possible
to run the same in production for relatively longer but not
extensive production runs. On the other hand, removing the
mold-closing compressive stresses from the mold cavity half blocks,
and reinforcing the same laterally, enables the prototype molds to
be made of weaker materials, if desired, such as those that are
more readily adaptable for being made by using conventional rapid
prototyping systems.
Third Embodiment Water Manifold and Associated Half Mold Nest
Assembly
FIGS. 11, 12, 13, 14 and 15 illustrate a third embodiment of a
water manifold sub-assembly that may be substituted for the water
manifold plate sub-assembly 308 in the second embodiment half mold
and nest assembly 300, or in a modified fourth embodiment half mold
and nest assembly as indicated hereinafter with reference to FIGS.
18-20 of the drawings. The third embodiment mold cooling water
manifold plate 500 is somewhat similar to water manifold plate 308
of the second embodiment in having a recessed nest or pocket formed
in its front face by a planar back surface 502 recessed rearward
from the flanking front end faces 504 and 506 of plate 500, all of
which extend in a plane parallel to the back face 508 of manifold
plate 500 (FIGS. 11-13 and 15). The sides of the pocket recess in
plate 500 are defined by parallel side walls 510 and 512 that are
spaced from one another by a constant predetermined design distance
to receive with a clearance fit a mating mold cavity half block 76,
76' or the like in the pocket of manifold plate 500 and against the
pocket side walls 510 and 512 respectively. Again, the flat back
wall of the mating mold cavity half block will abut flat against
the recessed back wall surface 502 of the pocket when it is drawn
tightly thereagainst by tightening down the mold block mounting cap
screws that are threadably received in the associated cooling block
through-holes 514, 516, 518, 520 (FIGS. 11-13 and 15) and thereby
precision align the mold block to the cooling block.
Water cooling manifold plate 500 differs from water manifolds 56
and 308 in several respects. As a first differential feature,
manifold plate 500 is constructed such that the coolant supply and
return lines are connected directly into the water manifold 500
rather than traveling from the back plate 52 or 302 into the
cooling passageways of the water manifold. This feature eliminates
the need for coolant supply passages in these back plates, and
even, in some applications, the need for these back plates
altogether.
Secondly, the front faces 504 and 506 of plate 500 function as mold
standoff abutment surfaces. This feature thus eliminates the need
for rails 304 and 306 and associated standoff rods 362, 364, 384
and 386, or separate plates 68 and 70 that are provided with the
standoff abutment vent deflector ribs 73 and 75.
Thirdly, these "wide wing" portions of the plate also mount four
pairs of cooperative alignment pins and bushings that interengage
to produce alignment of the two cooperative mold cavity half blocks
in the closed condition of the mold fixture. This feature thus
eliminates the need for rails 62, 64 and 66 and associated pins
114-122 and associated bushings and bushing rails. Fixture set-up
time is thereby reduced and alignment accuracy is also enhanced by
mounting the pins and bushings directly in the water manifold plate
that also "nests" the associated half mold cavity block.
Fourthly, the mold cooling manifold plate is provided with a
shallow recess in the front face, sealed by a peripheral O-ring,
that is connected to a side ported venting passageway
in-mold-labeling (IML) system for controlled negative pressure
venting of the blow mold cavity of the half mold cavity part during
blow molding. This feature cooperates with venting of the mold
cavity to the backside of the half mold part for temporarily vacuum
adhering a label in the mold cavity that is to be transferred in
situ to the blown container during blow molding.
As to the water cooling feature, the cooling of the mold cavity in
the associated mold cavity half block (not shown), after the
blowing of the hot parison therein, is accomplished by providing a
liquid coolant circulating passageway system that is entirely
contained within the manifold plate 500 as a sealed system
communicating with the inlet and outlet ports 530 and 532 (FIGS. 11
and 13) provided in the right hand exterior side face 534 of plate
500. The coolant system in plate 500 preferably comprises six
vertical coolant conducting passageways 540, 542, 544, 546, 548 and
550 arrayed parallel with one another and internally adjacent most
of the area of the recessed front face 502 of plate 500 (FIG. 11).
Each of these passageways is preferably formed by drilling a blind
bore upwardly from the bottom face 552 of plate 500. The upper
blind end of passageway 540 terminates just above a horizontal
drilled blind bore coolant inlet supply passageway 554 (FIG. 11)
extending coaxially with inlet port 530 and intersecting at its
inner end the vertical passageway 540. The four middle vertical
passageways 542, 544, 546 and 548 are all equal length and
terminate at their upper blind ends just below of the top face 556
of block plate 500.
The upper ends of passageways 542 and 544 are interconnected by
drilling a blind bore 558 into end face 534 that intersects the
upper ends of passageways 542 and 544 and terminates in passageway
544. Likewise, the upper ends of passageways 546 and 548 are
interconnected by drilling a blind horizontal bore 560 into the
opposite end face 562 of plate 500 so as to intersect the upper
ends of passageways 548 and 546 and terminate in passageway 546
(FIG. 11). The lower ends of passageways 548 and 550 are
interconnected by drilling another blind bore 564 into end face 562
so as to coaxially and perpendicularly intersect the lower ends of
passageways 550 and 548 and terminate in passage 548. Finally,
still another blind bore 566 is drilled into side face 534
coaxially with passageways 540, 542, 544 and 546 adjacent the
bottom face 552 of the block so as to intersect all four of these
passageways and to terminate in passageway 546. Bore 566 intersects
passageways 540 and 542 adjacent their lower ends thus
interconnects these two passageways. However, fluid communication
between lower ends of passageways 542 and 544 is blocked by
inserting a cylindrical aluminum baffle 570 (FIG. 11) into a blind
horizontal bore 572 that is drilled into the back face 508 of plate
500 (FIGS. 12 and 15) to perpendicularly intersect the axis of
passageway 544 and overlap the adjacent passageways 542 and 544
(FIG. 11).
In order to provide an internal coolant return passageway from the
upper end of downstream vertical passageway 550, another long blind
end bore passageway 574 is drilled horizontally into left hand side
face 562, extends horizontally internally of block 500 below tapped
mounting holes 514, 516 and terminates adjacent but offset
rearwardly from outlet port 532. A short blind bore passageway 576
is drilled perpendicular to the axis of outlet 532 and terminates
below and to the right of tapped hole 516 (FIG. 11). A pair of
short horizontal blind bore connector passageways 580 and 582 are
drilled into the back face 508 of block 500 (FIGS. 11, 12 and 15).
Blind bore connector 580 intersects the upper end of vertical
passageway 550 as well as passageway 574 to thereby flow connect
these passageways 550. Blind bore connector 582 intersects passage
574 as well as outlet passage 576 to thereby connect the downstream
end of passage 574 with the short outlet passage 576 leading into
outlet port 532 (FIGS. 11-13). The entrance of the drilled blind
bore passageways 540-550, 572, 574, 580 and 582 are each
individually sealed by an associated welch seal disk plug seated in
an entranceway counterbore.
Manifold cooling plate 500 also serves as the alignment fixture for
aligning the cooperative mold cavity half blocks, that are mounted
face-to-face in the associated recessed pockets of the water
manifolds, upon mold closure by the mold fixture. For this purpose,
four alignment pin through-bores 600, 602, 604 and 606 are drilled
horizontally through block 500, one in each of its four comers, so
as to extend between rear face 508 and front faces 504 and 506. The
axes of pin bores 600 and 604 perpendicularly intersect the axes of
passages 560 and 558, respectively, and the axes of pin bores 602
and 606 similarly intersect the axes of passages 564 and 566,
respectively. Each of the pin bores 600, 606 is provided with a
coaxial counterbore at face 508 for receiving the head 610 (FIG.
14) of an associated alignment pin 612 that is inserted in the
associated pin bore 600-606 so as to protrude at its shrank free
end 614 a predetermined distance (e.g., 0.312 inches) beyond the
associated end faces 504, 506 of plate 500, as shown in FIG. 14
with reference to pin 612. A slightly larger diameter counterbore
616 (FIG. 14) is formed in bore 600 extending from the pin head
countersink in rear face 508 and onward through the intersection of
bore 600 with passageway 558. The resultant clearance space 618
formed between the pin shank 620 and counterbore 616 shortens the
axial length of the interference retention fit of pin 620 in pin
bore 600. The same construction is provided with respect to the
remaining three alignment pins (not shown) that are identical to
pin 612 and respectively received in alignment bores 602, 604 and
606.
It will be understood that the mating water manifold plate 500'
(FIG. 14) is constructed as the substantially identical mirror
image to plate 500,
but differs therefrom in that it serves as the bushing half
manifold plate to thereby mount alignment bushings that cooperate
with the alignment pins to assure that each of the half mold
cavities are aligned upon mold closure. For this purpose, as shown
in FIG. 14 only, manifold plate 500' is provided with a bushing
bore 630 that coaxially registers with pin bore 600 upon mold
closure and opens to a counterbore 632 that extends to the end face
or back face 508' of plate 500'. Bore 630 receives an alignment
bushing 634 having an external end flange 636 that seats on a
shoulder at the junction of bores 630 and 632. A backup sleeve 638
is affixed in counterbore 632 that serves to secure bushing 634
seated in place. The same is true for the mirror image coolant
passages in manifold plate 500' corresponding to passages 558, 560,
564 and 566 of plate 500 to thereby mount the alignment pins in
plate 500. Although not shown, blind bore passageways 558, 560, 564
and 566 are countersunk at their entrance ends for individually
receiving a welch plug seal at the ends of such passageways.
The aforementioned IML internal venting passageway system for the
associated mold cavity half block nested in manifold plate 500 (and
likewise as to the mating manifold plate 500') comprises a
horizontally extending blind passageway 650 and pipe threaded
counterbore port 652 opening into plate side face 534 (FIGS. 11 and
13). Three parallel passages 654, 656 and 658 (FIGS. 11, 12 and 13)
extend from common passage 650 out into a lower central region of a
venting surface 670 that may be flush with back face 502 or
recessed a slight distance rearwardly from the back face 502 of the
recess pocket of plate 500. Venting surface 670 is surrounded by a
peripheral groove 672 that receives an O-ring seated therein and
that protrudes therefrom slightly past flush relative to face 502.
Hence, when the associated mold cavity half block is mounted by
suitable cap screws threaded in mounting openings 514-520 and drawn
tight against face 502, the surface 670 is sealed off by the O-ring
in groove 672 and thus provides a venting chamber that communicates
with the venting port passageways 654-658 that in turn lead to the
vent outlet port 652 in side 534. Thus, if the mold cavity half
block is provided with the usual pin hole vents D (such as shown in
conjunction with the prior art mold set-up of FIG. 2A described
previously hereinabove) that open into the back face of the mold
half, such pin hole vents will communicate with the chamber defined
by the boundary of surface 670 and the surrounding O-ring in groove
672. This sealed venting system thus can serve as a relief for
letting the air escape from the mold cavity as the parison is blow
expanded therein. Alternatively or in combination therewith, a
timed vacuum draw system can be coupled to port 652 to vacuum draw
and thereby temporarily adhere a label to the mold cavity surface
that will be transferred in situ to the blown container after
expansion thereof as the positive blow pressure is communicated
internally to the pinched parison tube. Alternatively, if desired,
the IML passageway system can be used to achieve a more controlled
expansion of the hot parison tube may thus be achieved by strategic
placement of the pin hole vents coupled with a synchronized
valve-controlled vacuum exhaust system that communicates with the
pin hole vents.
Manifold plate 500 is suitably removably affixed to a backing plate
or platen by suitable machine cap screws that thread into four
tapped blind mounting holes 680, 682, 684 and 686 formed in the
rear face 508 of plate 500 (FIGS. 11-13 and 15). In addition, a
central, vertically extending keyway slot 690 is provided in the
rear face 508 of plate 500 to receive key stock for alignment with
an associated key and key slot of the mounting plate to which
manifold plate 500 is fastened in the mold nest fixture
assembly.
In view of the foregoing novel features of the third embodiment
water manifold plate 500 that distinguish it from the previously
described first and second embodiment water manifold plates 56 and
308, it is to be understood the water manifold plate 500
constitutes one of the presently preferred embodiments of the
invention as illustrated herein.
Third Embodiment Mold Nest Fixture Assembly
FIGS. 16 and 17 illustrate a third embodiment of a mold nest
fixture assembly of the invention which is similar the first
embodiment fixture assembly of FIGS. 3-7, but modified with respect
to the smasher plate portions and water manifold backing plate
portion. Those components of the third embodiment fixture assembly
700 identical to components in fixture 50 of FIGS. 3-7 are given
identical reference numerals and the description not repeated.
In comparing fixtures 50 and 700, it will be noted that bottom
alignment rail 64 of fixture 50 and associated alignment pins 118,
120 have been eliminated from fixture 700 as not necessary to the
proper tryout functioning of the mold nest fixture embodiment 50 or
700 of the invention.
Secondly, the combination smasher plate and mold standoff
components 68 and 70, with their standoff and vent deflecting ribs
73 and 75, respectively, are modified in fixture 700 to provide
modified smasher plate assemblies 68' and 70'. Referring to smasher
plate assembly 70', it will be seen that the same is divided into a
standoff abutment back member 702 removably fastened to manifold
plate 56 and carrying the standoff abutment and vent deflecting rib
704 that corresponds to rib 75 of smasher plate 70. The front
parison-smashing surface is formed by a separate smasher plate
member 706 removably fastened to backing member 702. Plate 706 is
provided with beveled surfaces 708 and 710 at its upper and lower
edges to facilitate the parison smashing action during mold closure
and reduce the possibility of parison hang-up as a result of the
smashing action. The plate assembly 68' is constructed identically
to assembly 70'.
As will be well understood by those skilled in the art, the mold
nest fixture assemblies 50 and 700 are designed for use with a
Mueller tri-nest system in which three parison tubes are
simultaneously extruded from three parallel-oriented nozzles. The
central one of such nozzles aligns with the mold cavity 78, and the
outer two flanking parison tubes align with the smasher plates 68
and 70, or 68' and 70'. This feature of the prototype mold nest
fixtures 50 and 700 is provided because it is more economical to
run all three extruder nozzles even though using only a single
cavity mold for prototype tryout purposes. The mutually opposed
facing surfaces of the half mold nest assemblies, i.e., surface 69,
69' and its opposed surface of the other mold nest fixture, and
surface 71, 71' and its opposed mating surface on the other mold
nest fixture, are designed to be spaced a proper distance apart
upon mold closure to the mold closure plane of these two fixtures
to just squeeze the extruder parison flat. Hence a continuous
flattened tube is formed by successive mold closures cycle and fed
downwardly for retrieval as a continuous flattened length of scrap.
This features eliminates the problems of cutoff of the unused
flanking parison tubes, i.e., it avoids creating shavings and
pieces that tend to clog the components of the molding machine as
they fall by gravity.
A further modification found in fixture 700 versus fixture 50 is
the change in water manifold cover plate 58 and water manifold
support plate 60 of the cooling water manifold assembly 54. In
fixture 700, the same water manifold plate 56 is utilized but
components 58 and 60 are made as a one piece cover and support
plate 712. Plate 712 is removably fastened to plate 56 by a series
of 32 socket head cap screws 714 oriented in a peripheral array,
and by centrally disposed cap screws 716 recessed into a keyway
172' extending centrally and vertically in the backside of plate
712 for receiving keys 174 and 176.
The liquid sealing feature is obtained by providing a Parker O-ring
720 (FIG. 16) constructed and arranged as a peripheral seal to
replace the sealing weld 168 of fixture assembly 54. In addition,
each of the socket head caps crews 714, 716 is backed up by a welch
plug seal 722, as best seen in FIG. 17. The foregoing changes in
the water manifold assembly 54 enable removal of the backing plate
712 when needed for cleaning the coolant passages 158 or for
similar maintenance operations thereon.
Fourth Embodiment Mold Nest Fixture Assembly
Referring to FIGS. 18-23, a fourth embodiment of a mold nest
fixture assembly 800 is illustrated that is also constructed in
accordance with the principles of the present invention. Assembly
800 is similar to the second embodiment fixture assembly 300 of
FIGS. 8-10 with the exception that: (1) the inlet and outlet
coolant supply lines are connected to inlet and outlet ports 802
and 804 provided in the right hand side of a modified water cooling
manifold plate 308' (shown in nest assembly in FIGS. 18-20 and by
itself in FIGS. 21-23). Inlet port 802 connects via a horizontal
through-passageway 803 to inlet passage 452' (FIGS. 21-23) and
outlet port 804 connects via a horizontal through-passageway 805 to
outlet passage 460' of the serpentine coolant passageway 440 of the
manifold plate. The left-hand ends of passageways 803 and 805 are
sealed by inserting suitable Welch seal plugs. By thus providing
the coolant connections direct to the water cooling manifold plate
308', the cooling passageways 442, 444, 446, etc., provided in the
backing plate 302 of fixture embodiment 300 can be eliminated to
thereby simplify the backing plate 302' provided to cooperate with
water manifold plate 308'.
To further simplify backing plate 302', the alignment and standoff
rails 304 and 306 of fixture assembly 300 may be eliminated and
alignment bushing pins mounted in two upper comer openings 810 and
812 of packing plate 302'. The standoff abutment function is then
performed by the front face of the half mold cavity part 76' and
its mirror image companion part in the other nest assembly fixture.
Of course, backing plate 302' can be provided with the mounting
keyways and with the standoff rails 304 and 306 and associated
alignment pins and bushings and standoff rods, if desired, in the
manner of fixture assembly 300 described previously.
Preferably the inner vertical edges 403 and 405 of the nest "wing"
faces 402' and 404' are beveled faces. Manifold plate 308' is
removably fastened to backing plate 302' by the four socket head
cap screws 312, 314, etc., inserted in the four associated comer
mounting holes 315, the same as in the case of plate 308.
* * * * *